Ibrutinib likely works by blocking BTK or Bruton’s Tyrosine Kinase in the cancer cells. The minimum dose needed to inhibit BTK is 2.5 mg/kg/day, so if one weighs 80 kilograms or 174 pounds, then the minimum dose needed would be 200 mg/day. The recommended dose for CLL/SLL is 3 capsules of 140 mg. each for a total of 420 mg. daily providing a wide margin of safety. Since each capsule contains 140 mg, only two would exceed the required inhibitory dose for our theoretical 80 kilo patient. That said, there is limited data on the efficacy of taking a reduced dose and we do not recommend reducing the dose unless so advised by your treating physician. This is sometimes done to reduce some side effects that are dose dependent.
There have been only 75 reported cases of CLL in the last 10 years in South Korea, a country with a population of more than 50,000,000. We don’t know why CLL is less common in Asia.
Most CLL patients have had some impaired immunity for years before they are diagnosed.